This week’s TIME cover story, “The Mother of the Mitt Campaign,” tells the tale of how Lenore Romney’s 1970 run for U.S. Senate may have made a bigger impression on the Republican presidential candidate than his years spent as the son of a governor. Mitt’s father lost his own presidential bid, but it was the lessons from his mother’s loss that are more instructive as Romney enters the campaign stretch.

TIME’s Bart Gellman and Elizabeth Dias spent five months investigating this account and drew upon thousands of pages of correspondence, campaign archives, and audio and video recordings in the University of Michigan’s Bentley Historical Library; private documents and photographs held by participants in the events described and by authors Christian Goos and Sara Fitzgerald; and interviews with friends, relatives and other Romney contemporaries.

Rare photos of Mitt and his mom on the campaign trail by then-LOOK Magazine photographer Douglas Gilbert give an intimate look at young Mitt, then a newlywed, 23-year-old college senior. This was a Mitt who travelled every one of Michigan’s 83 counties in a blue truck with a Lenore logo, a Mitt who dodged a pie to the face on his mother’s behalf at a town festival, and a Mitt who said he’d want to be independent financially before he’d consider a political career. And above all, this was a Mitt whose learned caution is shaping the Republican party in 2012.

Here’s a taste:

No presidential nominee until now has grown up with two parents who ran for high office or so much early exposure to the craft. Their public ruin seared him and schooled him. The lessons he drew have shaped his ambitions, his calculations of risk and his strategy for achieving what hismother and father could not. Bluntly put, Mitt learned from each of his parents how to lose an election. He found much to emulate as well, but longtime associates and family members say it became his prime concern to avoid their mistakes. As he constructed a political persona, they say, his father’s career naturally loomed large—but ultimately his choices owed more to Lenore than to George.

Read the whole thing online Thursday, or pick up a copy from newsstands Friday.